1. Field of the Invention
The invention generally relates to a liquid crystal display (LCD) panel, and more particularly, to an LCD panel having the privacy protecting function.
2. Description of Related Art
Recently, the display device is required to have the wide-viewing characteristic when displaying images so as to satisfy the demand that a plurality of users simultaneously watches the displayed images of the same display device. Nevertheless, under certain conditions, such as writing business information or inputting personal account number and password into the ATM machine, the wide viewing characteristic of the display device may cause the reveal of user's personal information. Accordingly, the display device needs the privacy protecting designs for preventing the highly confidential data from being seen.
At present, a privacy protecting design is provided and achieved by using the alignment design of the LCD panel. In such privacy protecting technology, the LCD panel is used for providing the displaying function in the display device. Generally, the LCD panel is disposed between two polarizers, while the directions of the light transmission axis of the two polarizers respectively are configured parallel to the line direction and the row direction in the pixel array of the LCD panel. Namely, the light transmission axes of the two polarizers are restrictedly located in 0 degree azimuth angle and 90 degree azimuth angle and the light transmission axes of the two polarizers are included with each other by 90 degrees. Meanwhile, the LCD panel is divided into two regions such as the first region and the second region.
The changes of brightness with variant polar viewing angles and variant azimuth viewing angles have different tendencies in the first region and the second region of the LCD panel. Herein, the polar viewing angle means the included angle between the watching direction of the user and the baseline when the normal viewing angle direction (defining 0 degree polar viewing angle) is served as the baseline (i.e. the normal line of the LCD panel) and the azimuth viewing angle means the included angle in the horizontal surface between the watching direction of the user and a horizontal axis direction. By using such design, the LCD panel can have the privacy protecting function. The brightness distribution of the known LCD panel under different polar viewing angles is described in the following.
FIG. 1 shows the relationship between the displayed brightness presented by a conventional LCD panel under the privacy protecting mode and the corresponding polar viewing angles when the LCD panel is watched at variant polar viewing angles along the horizontal axis direction (that is, the direction parallel to the 0 degree azimuth viewing angle or the 180 degree azimuth viewing angle). Referring to FIG. 1, the curve 110 shows the relationship between the displayed brightness presented by the first region of the LCD panel and the polar viewing angles when the LCD panel under the privacy protecting mode is watched at variant polar viewing angles along the horizontal axis direction and the curve 120 shows the relationship between the displayed brightness presented by the second region of the LCD panel and the polar viewing angles when the LCD panel under the privacy protecting mode is watched at variant polar viewing angles along the horizontal axis direction, wherein the polar viewing angle at the normal viewing angle direction is, for instance, defined as 0 degree and the normal viewing angle direction means that the watching direction of the user is perpendicular to the outer surface of the substrate of the LCD panel. Herein, the normal viewing angle direction is defined as the position of the 0 degree polar viewing angle and the outer surface of the substrate of the LCD panel is defined as the position of the 90 degree polar viewing angle.
As shown in the curve 110 and the curve 120, the brightness presented in the first region is identical to the brightness presented in the second region when the watching direction is located at the normal viewing angle direction (that is the 0 degree polar viewing angle). Accordingly, the user can see the clear displayed image if the two eyes of the user both receive the display image in the normal viewing angle direction. Comparatively, at the polar viewing angle P1, the brightness presented in the first region as shown in the curve 110 is relatively weak while the brightness presented in the second region as shown in the curve 120 is relatively strong. Therefore, the user who watches the displayed image at the polar viewing angle P1 can merely see the unclear image information, thereby the privacy protecting effect can be achieved. It is noted that the user can see the complete image information merely when he or she watches the displayed image in the normal viewing angle direction and the user who watches the displayed image in the side viewing angle direction can only see the unclear image information. Therefore, the privacy protecting mode can be called as a narrow viewing angle display mode.
Specifically, as presented by the curve 110 and the curve 120, the first region and the second region present the same displayed brightness only when the polar viewing angle is 0 degree. Nevertheless, practically, the polar viewing angle that the user watches the image displayed by the display panel in the normal viewing angle direction may be located at the range from the angle P2 to the angle P3, such as the angle including the 0 degree normal viewing angle by ±5 degrees owing that the two eyes of the user are separated from each other by a distance. That is to say, the two eyes of the user located in the normal viewing angle direction see the image presented by the LCD panel at the angles adjacent to the normal viewing angle rather than right at the normal viewing angle in the real circumstance. In the meantime, the brightness received by the two eyes of the user differs from each other so that the user located in the normal viewing angle direction may feel giddy when watching the displayed image. In summary, the privacy protecting mode, i.e. the narrow viewing angle display mode, though prevents from the reveal of the personal information, causes uncomfortable feeling of the user in the normal viewing angle direction.